1. Field of the Invention
The present invention relates to management of when to replace a laser diode that has become weak.
2. Description of the Related Art
Laser diodes are used in optical communications and optical systems such bar-code readers. The laser diodes are small and they produce considerable laser output at low cost. However, the output of a laser diode decays with aging. In that case, it is the time to replace the laser diode with a new one.
Japanese Patent Application Laid Open No. 2001-092920 discloses a technology to determine when to replace the laser diode. Precisely, output of the laser diode is monitored and if the output is less than a specific value, it is determined that the laser diode should be replaced. However, according to this configuration, it is possible to determine when to replace the laser-diode only when the laser diode has become weak. Moreover, device can not be used from when it is determined that the laser diode needs replacement until the laser diode is replaced with a new one.
However, decay of the output of the laser diode is not only due to the aging of the laser diode. The output of the laser diode may also decay due to failure of a driving circuit that drives the laser diode. However, with the known technology, it is possible to decide whether the output of the laser diode has decayed due to the aging of the laser diode or failure of the driving circuit.